What is the Epley Formula?
The Epley formula is the most widely used method for estimating one-rep max (1RM) in strength training. Developed by A.S. Epley in the 1980s, it's the default formula in most fitness apps and online calculators, including our deadlift 1RM calculator.
How It Works
The formula takes the weight you can lift for multiple repetitions and estimates what you could lift for one rep. The relationship is non-linear - as the number of reps increases, the estimated 1RM increases but at a decreasing rate.
Example Calculation:
If you can deadlift 315 lbs for 5 reps:
1RM = 315 × (1 + 0.167)
1RM = 315 × 1.167
1RM = 367.5 lbs (167 kg)
Why is Epley the Most Popular?
- Simple to use: Easy mathematical calculation
- Well-validated: Tested across many studies and athletes
- Conservative estimates: Generally provides realistic predictions
- Industry standard: Used by most fitness professionals and apps
- Good accuracy: Most accurate for 1-10 rep ranges
When to Use Epley
Best For:
- • Intermediate lifters
- • 1-10 rep ranges
- • General fitness training
- • Powerlifting programs
Less Accurate For:
- • Very high reps (15+)
- • Elite athletes
- • Very light weights
Pro Tip
For the most accurate results, use weights you lifted for 1-8 reps. The Epley formula becomes less accurate with higher rep ranges where fatigue plays a bigger role.